Cellular phones, personal digital assistants, walkie-talkies, garage door openers, computers, wireless routers and other communication devices all incorporate radio technology to establish and maintain communications over the electromagnetic frequency spectrum. Some radio frequency (RF) devices, such as cordless telephones, may automatically search for a channel from among those channels assigned for use by the device to establish communications and then release the channel when the radio is finished. However, such devices are unable to automatically adapt to significant or challenging changes within the network or spectrum environment such as those discussed below.
Networked radios and other devices designed to operate within one particular channel or set of channels cannot operate outside of the designated channels without appropriate authorization from regulatory authorities or spectrum owners and/or modification of the radios. For example, a radio may search a specified band to find an open channel for communications with the network. The radio will sequentially or randomly step or hop through the band until an open channel is found or an indication is given (e.g., through a control signal) that the network is otherwise busy (e.g., no channels are available). Such a radio, however, does not determine a new band or frequency range from which to search for channels if a channel is not found. Rather, the radio either works within its prescribed frequency band according to its fixed characteristics (such as transmit power, bandwidth, and modulation scheme), or it does not work at all.
If a typical radio confronts interference, then its communications signals may not be transmitted or received. The radio also might receive a command from a base station to shut down for any number of reasons. As a specific example, under U.S. government regulations, radios operating on certain frequencies in the 5 GHz band must cease transmissions on that channel within a specified time from the detection of radar signals, which have priority over radio transmissions. A typical radio communication system, however, is not able to adjust its own operation, and typically cannot independently determine how to overcome interference problems such as harmful interference that may endanger the functioning of the system, or degrade, obstruct, or repeatedly interrupt service.
Some radios, known as software-defined radios, can be reconfigured using user-defined parameters and software-based mechanisms. These radios, however, are not able to dynamically adjust their operating behavior outside of a predetermined, fixed set of parameters without uploading new software to the radio or modifying its hardware.